There continues to be an existing need for generating electrical power inexpensively without creating pollution. The flow of water in rivers, channels, and streams provides a very large source of green energy that can be converted into electrical power.
The first records of water wheels as a valuable source of power date from the early ages of the new era. They have been considered as a primary source of power until the end of 18th century until the introduction of high pressure steam engines.
Water wheels evolved through history from simple stream wheels to more complex wheels of different types. Much effort went into the scientific investigation of water wheel efficiency, increasing it by a factor of three in the 18th century.
Due to their simplicity and justifiable application at low head sites, water wheels remained an important source of power until today. Indeed, for the past two decades, worldwide trends of increased environmental awareness favor and encourage continuation of extensive development and utilization of new water wheel types, attributing all the benefits of water wheel systems.
Despite the variety of water wheel types known today, they are commonly classified as A) an undershot type water wheel (FIG. 1A); B) a breastshot type water wheel (FIG. 1B); and C) an overshot type water wheel (FIG. 1C). These water wheels are typically installed land (i.e. not floating water wheels) and are supplied flowing water by an open water channel constructed on land to carry and direct the flowing water from a river or stream to the water wheels.
The water channel of the undershot water wheel (FIG. 1A) has a fixed depth before and after the water wheel at the fixed height reference points shown. The water channel of the undershoot water wheel (FIG. 1B) has a fixed depth before and after the water wheel at the reference points, however, the height of the second reference point is lower than the height of the first reference point. Further, the flow channel curved downwardly (i.e. partial circle) underneath the water wheel to combine forces due to both water flow and water weight to turn the water wheel. The water channel of the overshot water wheel (FIG. 1C) has a fixed depth before and after the water wheel at the reference points, however, the height of the second reference point is lower than the height of the first reference point. Further, the flow channel is discontinuous so that the water flow exits the water channel and directed to an upper portion of the water wheel to combine forces due to both water flow and water weight to turn the water wheel. Typically, the water channels have a fixed cross-sectional profile (e.g. fixed rectangular shape) along the length of the water channel.
Each of the above water wheel types has its own advantages and disadvantages. Traditional undershot water wheel (FIG. 1), also known as the oldest water wheel type, makes use of only water flow kinetic hydro potential and having the lowest efficiency, which means that it generates less power and can only be used where the flow rate is sufficient to provide torque. The breastshot and overshot water wheels, and some subtypes of undershot water wheels (e.g. Poncelet wheel, Zuppinger wheel) make use of both, gravitational and kinetic hydro potential of the water flow, consequently increasing the efficiency and amount of generated power. However, traditional undershot wheels are cheaper and simpler to build, and have less of an environmental impact due to simpler construction of the water channel. They are suitable for shallow streams in flat country.